Vehicles travel along a route from one location to another. Some vehicles travel along the route in an automatic mode in which, prior to traveling along the route, a controller predetermines one or more vehicle parameters, such as speed and throttle, pedal, or notch setting, for example, at each location along the route. In order to predetermine the vehicle parameter(s) at each location along the route, the controller may use a memory which prestores a characteristic of the route at each location, such as the grade, for example. While traveling along the route, the controller may need to be aware of the vehicle location to ensure that actual vehicle parameter(s) track or match the predetermined vehicle parameter(s) at each vehicle location. Additionally, since the route may include various vehicle parameter restrictions at various locations, such as a speed restriction, for example, the controller may need to be aware when the vehicle location is approaching a location of a restriction in order to adjust the vehicle parameter(s), if needed, to comply with the vehicle parameter restriction.
Alternatively, the vehicle may travel along the route in a manual mode, in which the vehicle operator is responsible for manually adjusting the vehicle parameters. As with the automatic mode, while traveling along the route, the vehicle operator may need to be aware of the vehicle location, such as when the vehicle location approaches a restriction location, for example. The vehicle operator can then manually adjust the vehicle parameter(s) to comply with a vehicle parameter restriction.
Some known systems have been designed to assist the controllers in the automatic mode and the vehicle operators in the manual mode by providing locations of the vehicle as the vehicle travels along the route. These systems, however, may rely solely on a global positioning satellite (GPS) system, which provide one measurement of the vehicle location based on satellite positioning, or other positioning systems using wireless network or wayside equipment, to provide raw position measurements of the vehicle. Upon receiving the positioning system measurement, the controller uses an internal memory to convert this raw position measurement to a distance measurement of the vehicle along the route.
As with any measurement system, such position measurement systems are capable of error, such as if a GPS receiver of the vehicle fails to communicate with a sufficient number of satellites in the GPS system or an error in the memory of the controller which may convert an accurate raw position measurement to an inaccurate distance measurement along the route, for example. Accordingly, it would be advantageous to provide plural independent distance measurements, such as an independent distance or position measurement in addition to a GPS measurement of the distance of the vehicle along the route, so to ensure that the distance estimation provided to the controller or vehicle operator is reliable. Additionally, it would be advantageous to assign a quality value to the distance estimation provided to the controller or vehicle operator.